With radio-frequency circuit elements, transmission lines play a central role in piping electrical signals from one place to another within a circuit. To avoid undesirable reflections, the load should present an impedance equal to the characteristic impedance of the line, referred to as matching the load to the line. Known baluns, which perform this function while interfacing the line to the load, typically comprise transformer coupled windings on a ferrite core which provide fixed impedance transformations from line to load (1:1 and 4:1 are common). There are applications, however, where it would be desirable to achieve arbitrary impedance transformations, preferably with a low insertion loss. To my knowledge, baluns with these capabilities are not currently available.